Spectroscopic Investigation of Cr(III)- and Cr(VI)-Treated Nanoscale Zerovalent Iron

Journal Article · Thu Jun 05 04:00:00 EDT 2008 · Environ. Sci. Technol.

DOI:https://doi.org/10.1021/es061721m· OSTI ID:1007556

Manning, Bruce A; Kiser, Jon R; Kwon, Hancheol; Kanel, Sushil Raj ^[1]

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1. UIUC

The reaction of hexavalent chromium (Cr(VI)) with zerovalent iron (Fe{sup 0}) during soil and groundwater remediation is an important environmental process. This study used several techniques including X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy to investigate nanometer scale Fe{sup 0} particles (nano Fe{sup 0}) treated with Cr(III) and Cr(VI). X-ray diffraction and XPS analyses of oxidized nano Fe{sup 0} showed the crystalline Fe(III) phase is composed of lepidocrocite ({gamma}-FeOOH). Results of XPS Cr 2p data and Cr K-edge X-ray absorption near edge spectroscopy (XANES) provided evidence that Cr(VI) was entirely reduced to Cr(III) by nano Fe{sup 0} with no residual Cr(VI) after reaction. In addition, XPS and XANES results of Cr(III) precipitated as Cr(OH){sub 3} in the presence of corroding nano Fe{sup 0} were nearly identical to the Cr(VI)-nano Fe{sup 0} reaction product. Detailed analysis of XPS O 1s line spectra revealed that both Cr(III)- and Cr(VI)-treated nano Fe{sup 0} yielded a predominantly hydroxylated Cr(OH){sub 3} and/or a mixed phase Cr{sub x}Fe{sub 1-x}(OH){sub 3} product. The structure of the Cr(III)- and Cr(VI)-treated nano Fe{sup 0} determined using extended X-ray absorption fine structure spectroscopy (EXAFS) revealed octahedral Cr(III) with Cr-O interatomic distances between 1.97 and 1.98 {angstrom} for both Cr(III) and Cr(VI) treatments and a pronounced Cr-Cr second interatomic shell at 3.01 {angstrom}. Our results suggest that the reaction product of Cr(VI)-treated nano Fe{sup 0} is either a poorly ordered Cr(OH){sub 3} precipitate or possibly a mixed phase Cr{sub x}Fe{sub 1-x}(OH){sub 3} product, both of which are highly insoluble under environmental conditions.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1007556
• Journal Information: Environ. Sci. Technol., Journal Name: Environ. Sci. Technol. Journal Issue: (2) ; 01, 2007 Vol. 41; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
ABSORPTION SPECTROSCOPY
CHROMIUM
FINE STRUCTURE
INTERATOMIC DISTANCES
IRON
SOILS
SPECTRA
SPECTROSCOPY
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY